High strength cryogenic high manganese steels and methods of making the same

ABSTRACT

Improved steel compositions and methods of making the same are provided. More particularly, the present disclosure provides high manganese (Mn) steel having enhanced strength and/or performance at cryogenic temperatures, and methods for fabricating high manganese steel compositions having enhanced strength and/or performance at cryogenic temperatures. The advantageous steel compositions/components of the present disclosure improve one or more of the following properties: strength, toughness, elastic modulus, thermal expansion coefficient and/or thermal conductivity. In general, the present disclosure provides high manganese steels tailored to resist wear and/or deformation at cryogenic temperatures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/346,069, filed on Jun. 6, 2016, the entire contents of which isincorporated herein by reference.

FIELD

The present disclosure relates to cost-effective high manganese steelstailored to achieve high yield strength, cryogenic toughness, and lowthermal stress. More specifically, the present disclosure pertains toferrous steel alloyed with a high amount (≧8 wt. %) of manganeseproviding high yield strength, cryogenic toughness, and low thermalstress and manufacturing the same. The strength, toughness, elasticmodulus, thermal expansion coefficient and thermal conductivity of thesesteels can be optimized through the control of microstructure andchemistry. The application of the present disclosure includes, but isnot limited to liquefied natural gas (LNG) storage, piping, and transferby pipeline.

BACKGROUND

Cryogenic structures such as liquefied natural gas (LNG) containervessels demand steels with specific low temperature properties. Thesteels need to remain ductile and crack resistant and must retain a highlevel of safety even at cryogenic temperatures (<−50° C.). These steelsmust also possess high strength in order to allow reduction of tank wallthickness which permits low cost construction. Conventional carbonsteels lose much of their toughness and become brittle at cryogenictemperatures. Steels commonly used for structural applications atcryogenic temperatures include alloy steels such as Fe-9 wt. % Ni steel,austenitic stainless steels (e.g., 304 SS with Fe-18 wt. % Cr-8 wt. %Ni), invar alloys (Fe-36 wt % Ni), and aluminum alloys.

Aluminum alloys are used in various cryogenic applications due to theirhigh specific strength and ductility. However, most aluminum alloys havelower strength compared with the strength of alloyed steel and arerelatively challenging to weld. Austenitic stainless steels (e.g., 304SS) and Invar alloys are relatively low strength and high cost.Nickel-alloyed high-strength steels (5% Ni and 9% Ni) provide acombination of high cryogenic strength and toughness and, hence, 9% Nisteels are often preferred for the most demanding low temperatureapplications. However, because of high Ni content, these alloys areexpensive.

Ferrous steels with high manganese (Mn) alloying can be a lower-costalternative to these cryogenic materials. The essential benefits of theinventive steels of the present disclosure are the lower cost byreplacing Ni with Mn, and higher strength due to higher carbon (C),and/or nitrogen (N) contents than the steels in the art.

Liquefied natural gas is usually transported by specially equipped shipsand stored in LNG-terminals. Conventional LNG carrier ships are of twobasic types. The first type (Moss type) uses heavy walledself-supporting spherical tanks made of aluminum to contain the LNG. Thesecond type (membrane type) uses a thin membrane of Invar alloy orcorrugated austenitic stainless steel supported by the ship's hull (withplywood and insulation in between) to contain the LNG. For export andimport terminals, free standing LNG storage tanks are typically made outof 9% Ni steel. In LNG tanks, cryogenic steels are joined by fusionwelding technology for liquid-tightness. Typical joining techniquesutilized in the field are GTAW (Gas Tungsten Arc Welding), GMAW (GasMetal Arc Welding), SMAW (Shielded Metal Arc Welding), and SAW(Submerged Arc Welding).

Even though extensive studies have been made on welding technologies forcryogenic steels, it remains challenging to cost effectively meet weldproperty requirements in cryogenic steel weldments. In the case of 9% Nisteel, for instance, achieving stable cryogenic toughness in theas-welded state (without heat treatment) can be challenging when aweldment is fabricated with similar composition filler wire. For thisreason, Ni-based alloy composition weld wire is typically used forjoining 9% Ni steels. Weldments with Ni-based alloy weld wire, however,show lower yield strength than that of 9% Ni steel itself, thuscompromising the full strength of the 9% Ni steel. Furthermore,weldments with Ni-based weld wires can be susceptible to hightemperature cracking (during welding) and fatigue damage due to adifference in thermal expansion coefficients. In addition, high nickelcontent increases the cost of welding consumables.

Traditional LNG loading/offloading lines of stainless steel requiremechanical expansion loops and bellows that can deflect with thermalstress to accommodate thermal contraction/expansion upon temperatureexcursion between construction and operating temperatures (refer to FIG.1). For LNG loading terminals, thus, a driving force exists to changeloading pipeline design from the standard jetty-based stainless steel toa system that does not require such accommodations (i.e., mechanicalexpansion loops and bellows).

By switching to alloys with higher yield strength and lower thermalexpansion coefficients, these expansion loops can be eliminated alongwith the above-sea trestle required to accommodate them. The lowercoefficient of thermal expansion (CTE) value decreases thermal stressesthat arise when the pipeline is cooled from ambient to operatingtemperature. Developing such pipelines with 9% Ni steel has beenattempted, but as for 9% Ni tanks designs, problems are incurred due tothe necessity of welding 9% Ni steel with undermatching, austeniticwelding consumables. The inventive concept of using high Mn steels(which can be welded with matching or overmatching weld consuambles) forcryogenic pipeline design allows for numerous advantages includingreduced materials and construction cost, increased pipeline security,reduced environmental impact, capital savings associated with jettyconstruction, and reduced operating costs.

SUMMARY

The present disclosure provides for a method for fabricating a ferrousbased component comprising: a) providing a composition having from about5 to about 40 weight % manganese, from about 0.01 to about 1.2 weight %carbon, and the balance iron; b) heating the composition to atemperature above the austenite recrystallization stop temperature ofthe composition or to a temperature to homogenize the composition; c)cooling the composition to a rolling start temperature; d) deforming thecomposition while the composition is at a temperature below theaustenite recrystallization stop temperature of the composition; and e)quenching the composition.

The present disclosure also provides for a ferrous based componentfabricated according to the steps comprising: a) providing a compositionhaving from about 5 to about 40 weight % manganese, from about 0.01 toabout 1.2 weight % carbon, and the balance iron; b) heating thecomposition to a temperature above the austenite recrystallization stoptemperature of the composition; c) cooling the composition to atemperature below the austenite recrystallization stop temperature ofthe composition; d) deforming the composition while the composition isat a temperature below the austenite recrystallization stop temperatureof the composition; and e) quenching the composition.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and aspects of embodiments are described below with referenceto the accompanying drawings, in which elements are not necessarilydepicted to scale.

Exemplary embodiments of the present disclosure are further describedwith reference to the appended figures. It is to be noted that thevarious steps, features and combinations of steps/features describedbelow and illustrated in the figures can be arranged and organizeddifferently to result in embodiments which are still within the spiritand scope of the present disclosure. To assist those of ordinary skillin the art in making and using the disclosed systems, assemblies andmethods, reference is made to the appended figures, wherein:

FIG. 1 is a diagram of a LNG loading line with expansion loop, asrequired using “traditional” (i.e., NOT the inventive high Mn steel ofthe present disclosure) piping technologies and/or piping compositions;

FIG. 2 is an exemplary diagram of the phase stability and deformationmechanism of high Mn steels as a function of alloy chemistry andtemperature;

FIG. 3 displays the predicted influence of alloying elements on the SFEvalues of the FeMn13C0.6 reference and the deformation mechanism;

FIG. 4 depicts the effect of carbide precipitates on mechanicalproperties and deformation mechanism (schematic, not in scale);

FIG. 5 is a schematic drawing of an exemplary steel fabrication methodof the present disclosure;

FIG. 6 depicts a schematic of an exemplary fabrication method forproducing ultrafine grained high Mn steels according to the presentdisclosure.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range is encompassed within the disclosure. Ranges from any lowerlimit to any upper limit are contemplated. The upper and lower limits ofthese smaller ranges which may independently be included in the smallerranges is also encompassed within the disclosure, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either both ofthose included limits are also included in the disclosure.

Although any methods and materials similar or equivalent to thosedescribed herein can also be used in the practice or testing of thepresent disclosure, the preferred methods and materials are nowdescribed. All publications mentioned herein are incorporated herein byreference to disclose and described the methods and/or materials inconnection with which the publications are cited.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “and”, and “the” include plural references unlessthe context clearly dictates otherwise.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this disclosure belongs. The terminology used in thedescription of the disclosure herein is for describing particularembodiments only and is not intended to be limiting of the disclosure.All publications, patent applications, patents, figures and otherreferences mentioned herein are expressly incorporated by reference intheir entirety.

Definitions

CRA: Corrosion resistant alloys, can mean, but is in no way limited to,a specially formulated material used for completion components likely topresent corrosion problems. Corrosion-resistant alloys may be formulatedfor a wide range of aggressive conditions.

Ductility: can mean, but is in no way limited to, a measure of amaterial's ability to undergo appreciable plastic deformation beforefracture; it may be expressed as percent elongation (% EL) or percentarea reduction (% AR).

Erosion resistance: can mean, but is in no way limited to, a material'sinherent resistance to erosion when exposed to moving solid particulatesstriking the surface of the material.

Toughness: can mean, but is in no way limited to, resistance to fractureinitiation.

Fatigue: can mean, but is in no way limited to, resistance to fractureunder cyclic loading.

Yield Strength: can mean, but is in no way limited to, the ability tobear load without deformation.

Cooling rate: can mean, but is in no way limited to, the rate of coolingat the center, or substantially at the center, of the plate thickness.

Austenite: can mean, but is in no way limited to, a solid solution ofone or more elements in face-centered cubic crystallographic structureof iron; the solute can be, but not limited to, carbon, nitrogen,manganese, and nickel.

Martensite: can mean, but is in no way limited to, a generic term formicrostructures formed by diffusionless phase transformation in whichthe parent (typically austenite) and product phases have a specificorientation relationship.

ε (epsilon)-martensite: can mean, but is in no way limited to, aspecific form of martensite having hexagonal close packed crystalstructure which forms upon cooling or straining of austenite phase.ε-martensite typically forms on close packed (111) planes of austenitephase and is similar to deformation twins or stacking fault clusters inmorphology.

α′(alpha prime)-martensite: can mean, but is in no way limited to, aspecific form of martensite having body centered cubic or body centeredtetragonal crystal structure which forms upon cooling or straining ofaustenite phase; α′-martensite typically forms as platelets.

M_(s) temperature: can mean, but is in no way limited to, thetemperature at which transformation of austenite to martensite startsduring cooling.

M_(f) temperature: can mean, but is in no way limited to, thetemperature at which transformation of austenite to martensite finishesduring cooling.

M_(d) temperature: can mean, but is in no way limited to, the highesttemperature at which a designated amount of martensite forms underdefined deformation conditions. M_(d) temperature is typically used tocharacterize the austenite phase stability upon deformation.

Carbide: can mean, but is in no way limited to, a compound of iron/metaland carbon.

Cementite: can mean, but is in no way limited to, a compound of iron andcarbon having approximate chemical formula of Fe₃C with orthorhombiccrystal structure.

Pearlite: can mean, but is in no way limited to, typically a lamellarmixture of two-phases, made up of alternate layers of ferrite andcementite (Fe₃C).

Grain: can mean, but is in no way limited to, an individual crystal in apolycrystalline material.

Grain boundary: can mean, but is in no way limited to, a narrow zone ina metal corresponding to the transition from one crystallographicorientation to another, thus separating one grain from another.

Quenching: can mean, but is in no way limited to, accelerated cooling byany means whereby a fluid selected for its tendency to increase thecooling rate of the steel is utilized, as opposed to air cooling.

Accelerated cooling start temperature (ACST): can mean, but is in no waylimited to, the temperature reached at the surface of plate, whenquenching is initiated.

Accelerated cooling finish temperature (ACFT): can mean, but is in noway limited to, the highest, or substantially the highest, temperaturereached at the surface of the plate, after quenching is stopped, becauseof heat transmitted from the mid-thickness of the plate.

Slab: a piece of steel having any dimensions.

Recrystallization: the formation of a new, strain-free grain structuregrains from cold-worked metal accomplish by heating through a criticaltemperature.

T_(nr) temperature: the temperature below which austenite does notrecrystallize.

The present disclosure provides advantageous steel compositions. Moreparticularly, the present disclosure provides improved high manganese(Mn) steel having high yield strength/cryogenic toughness/low thermalstress, and related methods for fabricating steel having enhanced yieldstrength/cryogenic toughness/low thermal stress. In exemplaryembodiments, the advantageous steel compositions/components of thepresent disclosure improve one or more of the following properties:yield strength, cryogenic toughness, thermal stress, elastic modulus,thermal expansion coefficient and/or thermal conductivity.

In general, the present disclosure provides for cost-effective highmanganese steels having improved performance during cryogenicapplications (e.g., yield strength, cryogenic toughness, thermal stress,elastic modulus, thermal expansion coefficient and/or thermalconductivity). More specifically, the present disclosure providesferrous steel alloyed with a high amount (e.g., greater than or equal toabout 5 weight %) of manganese, and where the fabricated steel exhibitsincreased/improved yield strength/cryogenic toughness/low thermal stress(e.g., improved yield strength, cryogenic toughness, thermal stress,elastic modulus, thermal expansion coefficient and/or thermalconductivity). The present disclosure also provides methods forfabricating such improved steel. In exemplary embodiments, the highmanganese steels of the present disclosure have advantages/potential inapplications where strength/toughness is desired/required at cryogenictemperatures.

In certain aspects, the disclosure provides methods for improving theyield strength, cryogenic toughness, and thermal stress of the steelsthrough the control of microstructure and/or chemistry. In certainembodiments, the methods include steps to promote phase transformations(e.g., to alpha prime martensite or epsilon martensite phases), twinningduring deformation, and/or introducing hard erosion resistant secondphase particles to the compositions.

Some exemplary uses/applications of the steel compositions of presentdisclosure include, without limitation, are use in piping systems,material conveying systems, fluids/solids transport systems, in miningoperations, and/or as material for liquefied natural gas (LNG) storagesystems, and piping for LNG onloading/offloading piping systems. Inanother aspect, the liquefied natural gas (LNG) storage systems, andpiping for LNG onloading/offloading piping systems are waffle-free,wrinkle-free, and/or free of expansion loop piping. Moreover, the use ofthe steels of the present disclosure can improve the economics of LNGstorage and/or transport.

Exemplary Methods for Fabrication

The present disclosure provides for a method for fabricating a ferrousbased component including: a) providing a composition having from about5 to about 40 weight % manganese, preferably from about 9 to about 25weight % manganese, even more preferably from about 12 to about 20weight % manganese, and from about 0.01 to about 1.2 weight % carbon,preferably from about 0.3% to about 1.2 weight % carbon, even morepreferably from about 0.3% to about 0.7 weight % carbon, and the balanceiron, b) heating the composition to a temperature above the austeniterecrystallization stop temperature of the composition (e.g., to atemperature to homogenize the composition); c) cooling to a rollingstart temperature (RST) d) deforming or hot rolling the compositionwhile the composition is at a temperature above the austeniterecrystallization stop temperature of the composition; and e) quenchingor accelerated cooling the composition.

The present disclosure provides for a method for fabricating a ferrousbased component including: a) providing a composition having from about5 to about 40 weight % manganese, preferably from about 9 to about 25weight % manganese, even more preferably from about 12 to about 20weight % manganese, and from about 0.01 to about 1.2 weight % carbon,preferably from about 0.3% to about 1.2 weight % carbon, even morepreferably from about 0.3% to about 0.7 weight % carbon, and the balanceiron, b) heating the composition to a temperature above the austeniterecrystallization stop temperature of the composition (e.g., to atemperature to homogenize the composition); c) deforming the compositionwhile the composition is at a temperature below the austeniterecrystallization stop temperature of the composition; and d) quenchingor accelerated cooling the composition. In another aspect, thetemperature recited in step c) is in the range of 700-1100° C.,preferably about 800-1000° C., and more preferably about 800-900° C.

The present disclosure provides for a method for fabricating a ferrousbased component wherein after step d), the matrix of the composition ispredominantly or substantially in the austenitic phase. In one or moreembodiments, the volume percent of austenite in the steel composition isfrom about 50 volume % to about 100 volume %, more preferably from about80 volume % to about 99 volume %, even more preferably from about 90volume % to about 98 volume %.

The steel composition is preferably processed into predominantly orsubstantially austenitic plates using a hot rolling process. In one ormore embodiments, a steel billet/slab from the compositions described isfirst formed, such as, for example, through a continuous castingprocess. The billet/slab can then be re-heated to a temperature (“reheattemperature”) within the range of about 1,000° C. to about 1,300° C.,more preferably within the range of about 1050° C. to 1250° C., evenmore preferably within the range of about 1100° C. to 1200° C.Preferably, the reheat temperature is sufficient to: (i) substantiallyhomogenize the steel slab/composition, (ii) dissolve substantially allthe carbide and/or carbonitrides, when present, in the steelslab/composition, and (iii) establish fine initial austenite grains inthe steel slab/composition.

The re-heated slab/composition can then be hot rolled in one or morepasses. In exemplary embodiments, the rolling or hot deformation can beinitiated at a “rolling start temperature”. In one or more embodiments,the rolling start temperature is above 1100° C., preferably above 1080°C., even more preferably above 1050° C. In exemplary embodiments, thefinal rolling for plate thickness reduction can be completed at a“rolling finish temperature”. In one or more embodiments, the rollingfinish temperature is above about 700° C., preferably above about 800°C., more preferably about 850° C. Thereafter, the hot rolled plate canbe cooled (e.g., in air) to a first cooling temperature or acceleratedcooling start temperature (“ACST”), at which an accelerated coolingstarts to cool the plates at a rate of at least about 10° C. per secondto a second cooling temperature or accelerated cooling finishtemperature (“ACFT”). After the cooling to the ACFT, the steelplate/composition can be cooled to room temperature (e.g., ambienttemperature) in ambient air. Preferably, the steel plate/composition isallowed to cool on its own to room temperature.

In one or more embodiments, the ACST is about 750° C. or more, about800° C. or more, about 850° C. or more, or about 900° C. or more. In oneor more embodiments, the ACST can range from about 700° C. to about1000° C. In one or more embodiments, the ACST can range from about 750°C. to about 950° C. Preferably, the ACST ranges from a low of about 650°C., 700° C., or 750° C. to a high of about 900° C., 950° C., or 1000° C.In one or more embodiments, the ACST can be about 750° C., about 800°C., about 850° C., about 890° C., about 900° C., about 930° C., about950° C., about 960° C., about 970° C., about 980° C., or about 990° C.

In one or more embodiments, the ACFT can range from about 0° C. to about500° C. Preferably, the ACFT ranges from a low of about 0° C., 10° C.,or 20° C. to a high of about 150° C., 200° C., or 300° C.

Without being bound by any theory, it is believed that the rapid cooling(e.g., more than about 10° C./sec cooling rate) to the low acceleratedcooling finish temperature (“ACFT”) retards at least a portion of thecarbon and/or nitrogen atoms from diffusing from the austenite phase ofthe steel composition to the grain boundary or second phase. It isfurther believed that the high accelerated cooling start temperature(“ACST”) retards at least a portion of the carbon and/or nitrogen atomsfrom forming precipitates such as, for example, carbides, carbonitrides,and/or nitrides during subsequent cooling to the ACFT. As such, theamount of precipitates at the grain boundaries is reduced. Therefore,the steel's fracture toughness and/or resistance to cracking and/orstrength at cryogenic temperatures are enhanced.

Following the rolling and cooling steps, the plate can be formed intopipes or the like (e.g., linepipe). Any suitable method for forming pipecan be used. Preferably, the precursor steel plate is fabricated intolinepipe by a conventional UOE process or JCOE process which is known inthe art.

The present disclosure also provides for a method for fabricating aferrous based component including: a) providing a composition havingfrom about 5 to about 40 weight % manganese, from about 0.01 to about1.2 weight % carbon, and the balance iron; b) heating the composition toa temperature above the austenite recrystallization stop temperature ofthe composition; c) cooling the composition to a temperature below theaustenite recrystallization stop temperature of the composition; d)deforming the composition while the composition is at a temperaturebelow the austenite recrystallization stop temperature of thecomposition; and e) quenching the composition.

The present disclosure also provides for a method for fabricating aferrous based component wherein after step e), the carbide precipitatefraction volume of the composition is about 3 volume % or less of thecomposition, preferably about 1.2 volume % or less of the composition,and even more preferably about 0.7 volume % or less of the composition.The present disclosure also provides for a method for fabricating aferrous based component wherein after step e), the composition has amicrostructure having a refined grain size of about 100 μm or less,preferably about μm or less, even more preferably about 30 μm or less.

The present disclosure also provides for a method for fabricating aferrous based component wherein the microstructure having a refinedgrain size of about 100 μm or less includes a surface layer of thecomposition. The present disclosure also provides for a method forfabricating a ferrous based component wherein the thickness of thesurface layer is from about 10 nm to about 5000 nm. The presentdisclosure also provides for a method for fabricating a ferrous basedcomponent wherein the surface layer is formed prior to or during the useof the composition. The present disclosure provides for a method forfabricating a ferrous based component wherein the surface layer isformed via a surface deformation technique selected from the groupconsisting of shot peening, laser shock peening, surface burnishing andcombinations thereof. The present disclosure provides for a method forfabricating a ferrous based component further including after step e) asurface deformation step selected from the group consisting of shotpeening, laser shock peening, surface burnishing and combinationsthereof.

The present disclosure provides for a method for fabricating a ferrousbased component wherein prior to step e), the composition is slowlycooled or isothermally held. The present disclosure provides for amethod for fabricating a ferrous based component wherein step e)includes rapidly quenching the composition. The present disclosureprovides for a method for fabricating a ferrous based component whereinstep d) includes deforming the composition while the composition is at atemperature below the austenite recrystallization temperature and abovethe martensite transformation start temperature.

The present disclosure provides for a method for fabricating a ferrousbased component wherein step d) includes deforming the composition toinduce martensite formation of the composition. The present disclosureprovides for a method for fabricating a ferrous based component whereinthe composition is deformed at a temperature of from about 18° C. toabout 24° C. to induce martensite formation of the composition. Thepresent disclosure provides for a method for fabricating a ferrous basedcomponent further including, after step d), heating the composition to atemperature above the austenite recrystallization stop temperature. Thepresent disclosure provides for a method for fabricating a ferrous basedcomponent wherein heating the composition to a temperature above theaustenite recrystallization stop temperature after step d) reversesdeformation-induced martensite of the composition into ultrafine grainedaustenite. The present disclosure provides for a method for fabricatinga ferrous based component wherein the martensite start temperature ofthe ultrafine grained austenite is below about 24° C.

The present disclosure provides for a method for fabricating a ferrousbased component further including, after step e), heating thecomposition to a temperature above the austenite recrystallization stoptemperature, and then quenching the composition. The present disclosureprovides for a method for fabricating a ferrous based component furtherincluding, prior to step c), deforming the composition while thecomposition is at a temperature above the austenite recrystallizationstop temperature. The present disclosure provides for a method forfabricating a ferrous based component wherein the composition isdeformed at a temperature of from about 700° C. to about 1000° C. Thepresent disclosure provides for a method for fabricating a ferrous basedcomponent wherein step b) includes heating the composition to at leastabout 1000° C. The present disclosure provides for a method forfabricating a ferrous based component wherein step c) includes coolingthe composition at a rate of from about 2° C. per second to about 60° C.per second.

The present disclosure provides for a method for fabricating a ferrousbased component wherein the composition further includes one or morealloying elements selected from the group consisting of chromium,aluminum, silicon, nickel, cobalt, molybdenum, niobium, copper,titanium, vanadium, nitrogen, boron, zirconium, hafnium and combinationsthereof.

The present disclosure provides for a method for fabricating a ferrousbased component wherein the chromium ranges from 0 to 30 weight % of thetotal composition, more preferably from 0.5 to 20 weight % of the totalcomposition, even more preferably from 2 to 5 weight % of the totalcomposition; wherein each of the nickel or cobalt ranges from 0 to 20weight % of the total composition, more preferably from 0.5 to 20 weight% of the total composition, even more preferably from 1 to 5 weight % ofthe total composition; wherein the aluminum ranges from 0 to 15 weight %of the total composition, more preferably from 0.5 to 10 weight % of thetotal composition, even more preferably from 1 to 5 weight % of thetotal composition; wherein each of the molybdenum, niobium, copper,titanium or vanadium ranges from 0 to 10 weight % of the totalcomposition, more preferably from 0.02 to 5 weight % of the totalcomposition, even more preferably from 0.02 to 2 weight % of the totalcomposition; wherein the silicon ranges from 0 to 10 weight % of thetotal composition, more preferably from 0.1 to 6 weight % of the totalcomposition, even more preferably from 0.1 to 0.5 weight % of the totalcomposition; wherein the nitrogen ranges from 0 to 3.0 weight % of thetotal composition, more preferably from 0.01 to 2.0 weight % of thetotal composition, even more preferably from 0.01 to 1.0 weight % of thetotal composition; wherein the boron ranges from 0 to 0.1 weight % ofthe total composition, more preferably from 0.001 to 0.1 weight % of thetotal composition; and wherein each of the zirconium or hafnium rangesfrom 0 to 6 weight % (e.g., 0.2 to 5 wt %) of the total composition.

The present disclosure provides for a method for fabricating a ferrousbased component wherein the composition includes from about 8 to about20 weight % manganese, from about 0.30 to about 0.7 weight % carbon,from about 0.5 to about 5 weight % chromium, from about 0.0 to about 2.0weight % copper, from about 0.01 to about 1 weight % silicon, and thebalance iron.

The present disclosure provides for a method for fabricating a ferrousbased component wherein step d) includes transformation inducedplasticity or twin-induced plasticity.

The present disclosure also provides for a ferrous based componentincluding a composition having from about 5 to about 40 weight %manganese, from about 0.01 to about 1.2 weight % carbon, and the balanceiron; and wherein the carbide precipitate fraction volume of thecomposition is about 2 volume % or less of the composition.

The present disclosure also provides for a ferrous based componentincluding a composition having from about 5 to about 40 weight %manganese, from about 0.01 to about 1.2 weight % carbon, and the balanceiron; and wherein the composition has a microstructure having a refinedgrain size of about 30 μm or less.

The present disclosure also provides for a ferrous based componentfabricated according to the steps comprising: a) providing a compositionhaving from about 5 to about 40 weight % manganese, from about 0.01 toabout 1.2 weight % carbon, and the balance iron; b) heating thecomposition to a temperature above the austenite recrystallization stoptemperature of the composition; c) cooling the composition to atemperature below the austenite recrystallization stop temperature ofthe composition; d) deforming the composition while the composition isat a temperature below the austenite recrystallization stop temperatureof the composition; and e) quenching the composition.

Any combination or permutation of embodiments is envisioned. Additionaladvantageous features, functions and applications of the disclosedsystems and methods of the present disclosure will be apparent from thedescription which follows, particularly when read in conjunction withthe appended figures. All references listed in this disclosure arehereby incorporated by reference in their entireties.

Exemplary Embodiments

The exemplary embodiments disclosed herein are illustrative ofadvantageous steel compositions, and systems of the present disclosureand methods/techniques thereof. It should be understood, however, thatthe disclosed embodiments are merely exemplary of the presentdisclosure, which may be embodied in various forms. Therefore, detailsdisclosed herein with reference to exemplary steelcompositions/fabrication methods and associated processes/techniques ofassembly and use are not to be interpreted as limiting, but merely asthe basis for teaching one skilled in the art how to make and use theadvantageous steel compositions of the present disclosure. Drawingfigures are not necessarily to scale and in certain views, parts mayhave been exaggerated for purposes of clarity.

The present disclosure provides advantageous steel compositions (e.g.,having enhanced strength/performance at cryogenic temperatures). Moreparticularly, the present disclosure provides improved high manganese(Mn) steel having high yield strength/cryogenic toughness/low thermalstress, and methods for fabricating high manganese steel compositionshaving high yield strength/cryogenic toughness/low thermal stress. Inexemplary embodiments, the advantageous steel compositions/components ofthe present disclosure improve one or more of the following properties:strength, toughness, elastic modulus, thermal expansion coefficientand/or thermal conductivity.

Representative properties of commercial cryogenic materials andinventive high Mn austenitic steels (i.e., high Mn steels of the presentdisclosure) are shown in Table 1.

TABLE 1 Typical properties of cryogenic materials and inventive steels.Cryogenic Inventive 9% Ni High Mn High Mn Properties 304L SS Al5083steel steel Steel Yield Strength (MPa) ≧190 ≧142 ≧585 ≧400 ≧600 UltimateTensile ≧420 ≧290 ≧690 ≧560 ≧1050 Strength (MPa) Charpy toughness (J@≧60 ≧30 ≧100 ≧82 ≧110 (@ −196° C.) −40° C.) ≧56 (@ −196° C.) Elasticmodulus (GPa) ~193 ~70 ~186 ~206 ~190 Thermal Expansion ~15 ~17 ~9-10~7.9-9.6 ~7.7-8.7 Coefficient (10⁻⁶ m/m ° C.) Thermal Stress (MPa) 552227 355 377 314 Thermal Stress/Y.S. ≦2.90 ≦1.60 ≦0.61 ≦0.94 ≦0.53Normalized cost to >2 >2 >2 1 ~1 HMS

The low elastic modulus of Al alloys maintains the thermal stress at afairly low level but still above the yield strength of the alloy. Thehigh elastic modulus and thermal expansion coefficient of the 304austenitic stainless steel and commercial cryogenic high Mn steel resultin high thermal stress well above the yield strength of the materials.While the thermal stress of 9% Ni and the inventive high Mn steels(i.e., high Mn steels of the present disclosure) are comparable, thehigh strength of the inventive high Mn austenitic steels (i.e., high Mnsteels of the present disclosure) makes it more capable as a materialfor LNG containment system and piping. Furthermore, the high Mn steelscan be welded with strength matching welding consumables, adistinguished advantage over 9% Ni steel design which are derated due tothe undermatched welds. Thus, the inventive high Mn austenitic steels ofthe present disclosure provide numerous advantages over the steels inthe art.

In one aspect, the disclosure provides methods for improving the yieldstrength/cryogenic toughness/thermal stress of the steels through thecontrol of microstructure and/or chemistry. In certain embodiments, theyield strength/cryogenic toughness/thermal stress of the steelcompositions of the present disclosure can be improved/increased throughthe control of microstructure and/or chemistry. Some such possibleroutes include promoting phase transformations (e.g., tomartensite/epsilon phases), twinning during deformation, and/orintroducing hard erosion resistant second phase particles to thecompositions.

In another aspect, the present disclosure provides high manganese steelstailored to resist wear and/or deformation (e.g., having improvedwear/deformation resistance properties) at cryogenic temperatures. Ingeneral, due to the high strength at cryogenic temperatures, the highmanganese steels of the present disclosure have advantages/potential inapplications where wear and/or deformation resistances at cryogenictemperatures are desired/required (e.g., LNG production, transportationand petrochemical applications).

In another aspect, the present disclosure provides high manganese steelstailored to resist wear and/or deformation (e.g., having improvedwear/deformation resistance properties) when used in applications thatrequire wear and/or deformation resistance during large temperaturevariations (e.g., from about −170° C. to about room temperature), suchas the temperature range experienced by a LNG storage tank and/or LNGpiping system when in use (e.g., about −170° C.) compared to when not inuse (e.g., room temperature). These properties are addressed by the highmanganese steels of the present application.

Any of the steel compositions as described or embraced by the presentdisclosure may be advantageously utilized in many systems/applications(e.g., piping systems, material conveying systems, fluids/solidstransport systems, in mining operations, and/or as material forliquefied natural gas (LNG) storage systems, and piping for LNGonloading/offloading piping systems), particularly where wear and/ordeformation resistances are important/desired at cryogenic temperatures.In exemplary embodiments, the systems/methods of the present disclosureprovide for low-cost and high strength steels (e.g., to be utilized invarious cryogenic LNG-related applications).

In another aspect, any of the piping systems, material conveyingsystems, fluids/solids transport systems, in mining operations, and/oras material for liquefied natural gas (LNG) storage systems, and/orpiping for LNG onloading/offloading piping systems presented herein maycomprise waffle-free or wrinkle-free LNG storage systems andexpansion-loop-free piping for LNG onloading/offloading piping systems.

In another aspect, the high Mn steels from any of the embodimentspresented herein exhibit a low coefficient of thermal expansion (CTE),low elastic modulus, and/or low bulk modulus.

Thermal stress due to thermal expansion and contraction of materialsfrom room temperature (25° C.) to service temperature (−163° C.) (i.e.,liquefied natural gas (LNG) storage and/or LNG onloading/offloading),σ_(thermal), can be calculated from the following equation:

σ_(thermal=) E·α·ΔT

where E is elastic modulus or Young's modulus, α is thermal expansioncoefficient, and ΔT is the temperature range from room temperature toservice temperature.

Cryogenic materials with lower yield strength, for which σ_(thermal)>σy,have to be designed with “waffle” or wrinkled design for membrane typeLNG storage tank and with expansion loops for cryogenic piping in orderto keep the thermal stress below the yield stress of the material.Another aspect of the present disclosure is that the inventive steelscan eliminate the necessity of wrinkled design or expansion loops incryogenic structures.

In another embodiment, the inventive high Mn austenitic steel provideshigh yield strength, σ_(y), which is higher than thermal stress for LNGapplications. In other words, σ_(thermal)<σ_(y). Preferably,σ_(thermal)<x·σ_(y) where x is smaller than 1. For example, x can be0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, or 0.5. Preferably, x issmaller than 0.8. More preferably, x is smaller than 0.7. Even morepreferably, x is smaller than 0.6.

In another embodiment, the inventive high Mn austenitic steel provideslow CTE, approximately lower than 12 (10⁻⁶ m/m° C.), and low elasticmodulus (e.g., elastic modulus lower than 210 GPa), whilst maintaininghigh strength (e.g., strength higher than 590 MPa).

In another embodiment, the inventive high Mn austenitic steel comprisesabout 0.3% to about 1.2% Carbon, and from about 8% to 30% Manganese.

In yet another embodiment of the current disclosure, the inventive steelis alloyed with microalloying elements such as Nb, V, Ti, Mo, W andother alloying elements such as Cr, C, and N to enhance yield strength.In another embodiment of the present disclosure, the inventive steelscan be welded with Ni-base weld wire (e.g., 625 Ni alloy) and/or high Mnalloyed weld wire.

In yet another embodiment, the inventive high Mn austenitic steels havea predominantly austentic structure stabilized at cryogenic temperature.The typical M_(d30) temperature, the highest temperature at which adesignated amount of martensite forms under 30% deformation conditions,of the inventive steels are below service temperature of LNG containmentsystem.

As discussed in further detail below, the fabrication methods/systems ofthe present disclosure can include one or more of the following steps:(i) providing a high work hardening rate matrix, through transformationinduced plasticity (“TRIP”) and/or twin-induced plasticity (“TWIP”);(ii) providing meta-stability to induce phase transformation duringservice; (iii) providing optimum hardness of martensite (e.g., to becontrolled by dissolved carbon content, to provide required erosionresistance); (iv) the dispersion of second phase particles (e.g.,carbides, quasi-crystals, etc.) of varying size ranges within thecompositions; (v) utilization of advantageous thermo-mechanicalcontrolled process (“TMCP”) fabrication steps/schemes (e.g., to achieveat least some of the steps above); and/or (vi) exemplary joiningmethods, such as solid state joining (e.g., Friction Stir Welding).

In general, the high manganese steels of the present disclosure arerelatively inexpensive alloys, and have potential applications wherewear and/or deformation at cryogenic temperatures or the like of workingcomponents is important. In certain embodiments, the steel compositionshave from about 0.30 to about 0.70 weight % carbon, and from about 11 toabout 20 weight % manganese.

In exemplary embodiments, the steel has a fully austenitic structureobtained by quenching from a temperature above about 1000° C. In thiscondition, the hardness of the material is relatively low. Oneparticularly advantageous feature of the high manganese steel is thestrong work hardening capability. Under impact or other mechanicalstress, the surface layer can increase its hardness rapidly bymartensitic transformation or twinning, whereas other portions/parts ofthe steel remain substantially soft and/or ductile. This combination oflow cost and high work hardening rate makes these steels advantageouslysuitable to be applied as wear resistant piping material at cryogenictemperatures or the like.

In general, the present disclosure provides for steels that exhibit acombination of high strength and erosion resistance. Also, as the resultof their good formability, the high manganese steels as described hereincan be used in a variety of settings, including, mining and automotiveapplications.

As noted, the present disclosure relates to high manganese steelchemistry and/or microstructures tailored to achieve improved strength,toughness, elastic modulus, thermal expansion coefficient and/or thermalconductivity. In exemplary embodiments, surface grain refinement maytake place in a surface layer of certain high Mn steels either prior toand/or during service/use (e.g., formed in-situ). For example, the grainrefinement at the surface can result in the formation of a layer whichpossesses the unique combinations of high strength and hardness, highductility, and/or high toughness. Such fine grained (e.g., about 100 nmlayer in height) or ultrafine grained (e.g., about 10 nm layer inheight) surface layer may be formed either prior to and/or duringservice/use (e.g., formed in-situ), and can impart the desired strength,toughness, elastic modulus, thermal expansion coefficient and/or thermalconductivity to the steel.

In exemplary embodiments, such fine grained (e.g., about 100 nm layer)or ultrafine grained (e.g., about 10 nm layer) surface layer may beformed prior to use/installation of the exemplary steel by such surfacedeformation techniques such as, without limitation, shot peening, lasershock peening, and/or surface burnishing.

Current practice provides that the mechanical loads against the pipes insome piping systems are not strong enough to cause the maximum workhardening of the steel. In exemplary embodiments, the present disclosureprovides high manganese steel with improved wear resistance, which canprovide pipes for piping systems with advantageous wear lifeexpectancies.

Current practice also provides that the steel in material conveyingsystems (e.g., piping systems, heavy equipment, etc.) often wears and/orfails prematurely, which leads to significant repair, replacement and/ormaintenance/production costs. In exemplary embodiments, the presentdisclosure provides high manganese steel with improved wear and/ordeformation resistance at cryogenic temperatures, which can providepipes for piping systems with advantageous life expectancies.

In additional exemplary embodiments, the present disclosure provides forferrous based components/compositions containing manganese. In certainembodiments, the components/compositions include from about 5 to about40 weight % manganese, from about 0.01 to about 1.2 weight % carbon, andthe balance iron. The components/compositions can also include one ormore alloying elements, such as, without limitation, chromium, nickel,cobalt, molybdenum, niobium, copper, titanium, vanadium, nitrogen, boronand combinations thereof. Exemplary ferrous basedcomponents/compositions containing manganese (and optionally otheralloying elements) are described and disclosed in U.S. Patent Pub. No.2012/0160363, the entire contents of which is hereby incorporated byreference in its entirety.

Component Composition

In exemplary embodiments and as noted above, the ferrous basedcompositions include from about 5 to about 40 weight % manganese, fromabout 0.01 to about 1.2 weight % carbon, and the balance iron.

As such, the manganese level in the compositions may range from about 5to 40 wt % of the total component/composition. The carbon level in thecomponent/composition may range from 0.01 to 1.2 wt % of the totalcomponent/composition. In general, iron constitutes the substantialbalance of the component/composition.

The components/compositions can also include one or more alloyingelements, such as, without limitation, chromium, aluminum, nickel,cobalt, molybdenum, niobium, copper, titanium, vanadium, nitrogen,boron, zirconium, hafnium and combinations thereof. Weight percentagesare based upon the weight of the total component/composition.

Chromium may be included in the component from about 0 to about 30 wt %(more preferably from 0.5 to 20 weight % of the total composition, evenmore preferably from 2 to 5 weight % of the total composition). Nickelmay be included in the component from about 0 to about 20 wt % (morepreferably from 0.5 to 20 weight % of the total composition, even morepreferably from 1 to 5 weight % of the total composition). Cobalt may beincluded in the component from about 0 to about 20 wt % (more preferablyfrom 0.5 to 20 weight % of the total composition, even more preferablyfrom 1 to 5 weight % of the total composition). Aluminum may be includedin the component from about 0 to about 15 wt % (more preferably from 0.5to 10 weight % of the total composition, even more preferably from 1 to5 weight % of the total composition. Molybdenum may be included in thecomponent from about 0 to about 10 wt % (more preferably from 0.2 to 5weight % of the total composition, even more preferably from 0.1 to 2weight % of the total composition). Silicon may be included in thecomponent from about 0 to about 10 wt % (more preferably from 0.1 to 6weight % of the total composition, even more preferably from 0.1 to 0.5weight % of the total composition). Niobium, copper, titanium and/orvanadium can each be included in the component from about 0.02 to about10 wt % (more preferably from 0.02 to 5 weight % of the totalcomposition, even more preferably from 0.02 to 2 weight % of the totalcomposition). Nitrogen can be included in the component from about 0.01to about 3.0 wt % (more preferably from 0.01 to 2.0 weight % of thetotal composition, even more preferably from 0.01 to 1.0 weight % of thetotal composition). Boron can be included in the component from about 0to about 0.1 wt % (more preferably from 0.001 to 0.1 weight % of thetotal composition).

The ferrous based components/compositions containing manganese may alsoinclude another alloying element selected from the group consisting ofzirconium, hafnium, and combinations thereof. Each of these otheralloying elements may be included in the component/composition in rangesfrom about 0 to about 6 wt % (e.g., 0.2 to 5 wt %) based on the totalweight of the component/composition.

In general, the mechanical properties of the high Mn steels of thepresent disclosure are dependent on the characteristics ofstrain-induced transformation, which is typically controlled by thechemical composition of the steels and/or the processing temperatures.Unlike conventional carbon steels, high Mn steels include a metastableaustenite phase with a face centered cubic (fcc) structure at ambienttemperature (e.g., 18-24° C.).

Upon straining, the metastable austenite phase can transform intoseveral other phases through strain-induced transformation. Moreparticularly, the austenite phase could transform into microtwins (fcc)structure (twin aligned with matrix), ε-martensite (hexagonal lattice),and α′-martensite (body centered tetragonal lattice), depending on steelchemistry and/or temperature.

These transformation products could impart a range of unique propertiesto high Mn steels. For example, fine microtwins effectively segmentprimary grains and act as strong obstacles for dislocation gliding. Thisleads to effective grain refinement which results in an excellentcombination of high ultimate strength and ductility.

Chemical composition and temperature are known to be primary factorscontrolling the strain-induced phase transformation pathways as shown inFIG. 1. In general, high Mn steels can be divided into four groupsdepending on the stability of austenite phase upon straining andtemperature, e.g., hilly stable (A), mildly metastable (B), moderatelymetastable (C) and highly metastable (D) Mn steel. The metastability ofthese phases is affected by both temperature and strain. These steelswould tend to be more metastable (e.g., higher tendency to transform) atlower temperatures and higher strains.

FIG. 2 is an exemplary diagram of the phase stability and deformationmechanism of high Mn steels as a function of alloy chemistry andtemperature. The letters (A, B, C, and D) indicate the various methodsof transformation during deformation. In this diagram, steel A woulddeform by slip (similar to other metals and alloys), while steels B-Dwould transform during deformation.

Steel in area A, with high Mn content (e.g., greater than or equal toabout 25 wt %), has stable austenite and deforms primarily bydislocation slip upon mechanical straining. In general, steels with afully stabilized austenitic structure show lower mechanical strength butremain tough at cryogenic temperatures, provide low magneticpermeability and are highly resistant to hydrogen embrittlement.

Steel in area B, which is mildly metastable, can be produced withintermediate manganese content (e.g., from about 15 to about 25 wt % Mn,and about 0.6 wt % C). These steels form twins during deformation. Alarge amount of plastic elongation can be achieved by the formation ofextensive deformation twins along with dislocation slip, a phenomenonknown as Twinning-Induced Plasticity (TWIP). Twinning causes a high rateof work hardening as the microstructure is effectively refined, as thetwin boundaries act like grain boundaries and strengthen the steel dueto the dynamic Hall-Petch effect. TWIP steels combine extremely hightensile strength (e.g., greater than 150 ksi) with extremely highuniform elongation (e.g., greater than 95%), rendering them highlyattractive for many applications.

The moderately metastable steels (Steel in area C) can transform intoε-martensite (hexagonal lattice) upon straining. Upon mechanicalstraining, these steels would deform predominantly by the formation ofε-martensite, along with dislocation slip and/or mechanical twinning.

The highly metastable steels (Steel in area D) will transform to astrong body-centered cubic phase (referred to as α′-martensite) upondeformation. This strong phase provides resistance to erosion resultingfrom the impingement of external, hard particles. Since the impact ofthe external particles results in the deformation of the near surfaceregions of the steel, these surface regions will transform duringservice, thereby providing resistance to erosion. Therefore, thesesteels have a “self-healing” characteristic in the sense that if thehard surface layer gets damaged, it would reform by the impact of theservice.

Thus, the chemistry of the high Mn steels can be tailored to provide arange of properties (e.g., wear resistance, cryogenic toughness, highformability, erosion resistance) by controlling their transformationduring deformation.

Other Alloying Concepts in High Mn Steels

Alloying elements in high Mn steels determine the stability of theaustenite phase and strain-induced transformation pathways. In general,manganese is the main alloying element in high Mn steels, and it isimportant in stabilizing the austenitic structure both during coolingand deformation. In the Fe—Mn binary system, with increasing Mn content,the strain induced phase transformation pathway changes fromα′-martensite to ε-martensite and then to micro-twinning.

Carbon is an effective austenite stabilizer and the carbon solubility ishigh in the austenite phase. Therefore, carbon alloying can be used tostabilize the austenite phase during cooling from the melt and duringplastic deformation. Carbon also strengthens the matrix by solidsolution hardening. As noted, the carbon in the components/compositionsof the present disclosure may range from about 0.01 to about 1.2 wt % ofthe total component/composition.

Aluminum is a ferrite stabilizer and thus destabilizes austenite phaseduring cooling. The addition of aluminum to high Mn steels, however,stabilizes the austenite phase against strain-induced phasetransformation during deformation. Furthermore, it strengthens theaustenite by solid solution hardening. The addition of aluminum alsoenhances the corrosion resistance of the high Mn containing ferrousbased components disclosed herein due to its high passivity. Thealuminum in the components/compositions of the present disclosure mayrange from about 0.0 to about 15 wt % of the total component.

Silicon is a ferrite stabilizer and sustains the α′-martensitetransformation while promoting ε-martensite formation upon deformationat ambient temperature. Due to solid solution strengthening, addition ofSi strengthens the austenite phase by about 50 MPa per 1 wt % additionof Si. The silicon in the components/compositions of the presentdisclosure may range from about 0.01 to about 10 wt % of the totalcomponent.

Chromium additions to high Mn steel alloys enhance the formation offerrite phase during cooling and increase corrosion resistance.Furthermore, the addition of Cr to the Fe—Mn alloy system reduces thethermal expansion coefficient. The chromium in thecomponents/compositions of the present disclosure may range from about0.5 to about 30 wt %. of the total component.

Based on the understanding of these alloying element effects onstrain-induced phase transformation, suitable steel chemistries can bedesigned for specific applications. Some criteria for the design of highMn steels can be the critical martensite transformation temperatures,e.g., M_(s) and M_(εs). M_(s) is a critical temperature below whichaustenite to α′-martensite transformation occurs, and M_(εs) is acritical temperature below which austenite to ε-martensitetransformation takes place.

The effects of alloying elements on M_(s) and M_(εs) can be expressed asfollows (unit of alloying elements in weight percent, and where A₃ is acritical temperature above which all ferrite phases (including α′- andε-martensite phases) transform to austenite):

M_(s)(K)=A₃-410-200(C+1.4N)-18Ni-22Mn-7Cr-45Si-56Mo; and

M_(εs)(K)=670-710(C+1.4N)-19Ni-12Mn-8Cr+13Si-2Mo-23Al

In general, only austenite to α′-martensite transformation takes placeif M_(s) is much higher than M_(εs). If M_(εs) is much higher thanM_(s), only austenite to ε-martensite transformation takes place. Bothα′-martensite and ε-martensite phase transformation occur if M_(s) andM_(εs) are close to each other.

It is noted that the ferrous based components/compositions containingmanganese may be utilized in a wide variety of applications/uses/systems(e.g., piping systems, material conveying systems, fluids/solidstransport systems, in mining operations, and/or as material forliquefied natural gas (LNG) storage systems, and piping for LNGonloading/offloading piping systems, materials for cryogenic gas (e.g.,Liquefied petroleum gas, Liquefied Ethylene gas, supercritical CO2)storage and piping, and cold liquid processing vessels and pipingincluding amine scrubber, and high pressure heat exchangers.

For example, as described and disclosed in U.S. Patent Pub. No.2012/0160363 noted above, the ferrous based components/compositionscontaining manganese of the present disclosure may find numerousnon-limiting uses/applications in the oil, gas and/or petrochemicalindustry or the like (e.g., cryogenic applications, corrosion resistantapplications, erosion resistant applications, natural gasliquefaction/transportation/storage type structures/components, oil/gaswell completion and production structures/components, subterraneousdrilling equipment, oil/gas refinery and chemical plantstructures/components, coal mining structures/equipment, coalgasification structures/equipment, etc.).

The relatively low alloying content (e.g., less than about 20 wt % Mn,and about 0.6 wt % C) produces the highly metastable austenite phase.The highly metastable austenite phase often transforms into hardα′-martensite upon straining, which typically is an irreversibletransformation. Upon surface wear of these steels, a surface layer ofthe highly metastable austenite phase can transform to α′-martensitephase. This friction-induced phase transformation leads to the formationof a thin, hard surface layer composed of martensite over an interiorthat consists of tough, untransformed austenite. This unique combinationrenders high Mn steels suitable for wear/erosion and impact resistantapplications.

Moreover, the joining of the high Mn steels of the present disclosurecan be performed using conventional (e.g., fusion, resistance welding,etc.) and emerging joining methods (e.g., laser, electron beam, frictionstir welding, etc.), as described and disclosed in U.S. Patent Pub. No.2012/0160363 noted above. In exemplary embodiments, preferred joiningmethods include solid state welding methods (e.g., resistance welding,friction stir welding), where such welding methods do not require theuse of a weld metal, although the present disclosure is not limitedthereto.

Bulk Modification

In exemplary embodiments, bulk modification is utilized to promote phasetransformation (TRIP) and twinning (TWIP) during deformation. Ingeneral, the dispersed particles strengthen the materials/compositions,but have complex effects. It is noted that the dispersed particles mayinfluence the: (i) chemistry of the composition matrix itself, (ii)grain size, and (iii) overall material/composition toughness. Ingeneral, the proper balance of these effects is important to exemplaryembodiments of the present disclosure.

High manganese steel generally has a rapid work hardening rate becauseof the TRIP/TWIP effects. Their activations are typically triggered bythe value of the stacking fault energy (“SFE”) of the alloy. It is notedthat the plastic deformation is associated with martensitictransformation at low SFE values (e.g., less than about 12 mJ/m²), andby twinning at intermediate SFE values. At even higher SFE values (e.g.,greater than 35mJ/m²), plasticity and strain hardening is typicallycontrolled solely by dislocation sliding. As such, the SFE value is animportant parameter in steel design.

The SFE is a function of alloy chemistry and temperature. The intrinsicstacking fault can be represented as a ε-martensite embryo of two planesin thickness. The SFE includes both volume energy and surface energycontributions. It has been demonstrated that the chemistry andtemperature dependence of SFE arises largely from the volume energydifference between ε-martensite and austenite. Moreover, the volume freeenergy of phases can be obtained from available databases or the like.

FIG. 3 shows the predicted SFE values when adding each alloying elementto FeMn13C0.6. Stated another way, FIG. 3 displays the predictedinfluence of alloying elements on the SFE values of the FeMn13C0.6reference and the deformation mechanism.

As shown in FIG. 3, the SFE contribution from the addition of variousalloying elements is different. Carbon has the strongest effect, andmanganese has the smallest influences. When the interaction of multiplealloying elements is considered, the dependence of SFE on chemistry willbe complex and non-monotonic. In general, the deformation mechanism canbe controlled by properly tailoring the bulk chemistry.

Second Phase Particle Dispersion Strengthening

In exemplary embodiments, the systems/methods of the present disclosurealso include the introduction of second phase particles to furtherimprove the wear resistance of the exemplary steel compositions. Incertain non-limiting embodiments the exemplary systems/methods aredescribed primarily with respect to carbide/nitride particles. However,it is noted that the systems/methods of the present disclosure mayutilize, apply to and/or include other particles/precipitates, such as,without limitation, borides and oxides. In exemplary embodiments, whenprimarily carbide/nitride and oxide particles are considered, the grainsize refinement can be an additional benefit from the second phaseparticles.

In general, the size and spatial distribution of the particles areimportant. It has been demonstrated that the effectiveness of theparticles on the steel/material strengthening increases with decreasingparticle size. Thus, fine particles generally contribute to the materialwear resistance largely by strengthening the materials, while coarseparticles typically provide additional resistance to erosive damage.

It is noted that the size and/or spatial distribution of the particlescan be adjusted or optimized based on materials service conditions. Forexample, for compositions for use in a piping system or the like, thewear damage may be caused by sands having wide particle sizedistribution. Therefore, a bimodal particle distribution could beconsidered for the steel composition. It is noted that the fabricationor manufacture of high manganese steel with various type and size secondphase particle can be achieved through various exemplarythermo-mechanical controlled processes (“TMCP”), as discussed furtherbelow.

In certain embodiments, the carbide/nitride precipitation can alsolocally enhance the TRIP or TWIP effects in the austenitic matrix. Theinterstitial elements (carbon and nitrogen) concentration incarbide/nitride particles is much higher than the average value of thesteel. Due to diffusion gradients at the interface, the interstitialelements could be depleted in precipitates surrounding the matrix, whichresults in a lower activation energy for TRIP or TWIP.

FIG. 4 (schematic, not in scale) displays the overall effect of carbideprecipitates on mechanical properties and the corresponding deformationmechanism. Compared to the fully austenitic steel with substantially thesame chemistry, the high manganese steel with the exemplarycarbide/nitride particles can have a higher yield strength and workhardening capability. In exemplary embodiments, the combination of hardparticles and a work-hardenable material matrix makes the compositionsof the present disclosure suitable to withstand and/or reduce theabrasive wear effects caused by operational use (e.g., by hard particlecutting/shearing or the like).

Fabrication and Microalloying

The steel compositions/components of the present disclosure can befabricated or manufactured by various processing techniques including,but not limited to, various exemplary thermo-mechanical controlledprocessing (“TMCP”) techniques, steps or methods. In general, some TMCPprocesses have been utilized to produce low alloy steel, particularlywhere grain size and microstructure refinement is desired.

In exemplary embodiments, to produce the desired carbide/nitrideparticles, the particles should be in a substantially dissolved statebefore the deformation, as undissolved particles will suffer relativelyrapid coarsening at the elevated temperatures. The controlleddeformation should take place below the recrystallization stoptemperature so that deformation results in elongated austenite grainsfilled with intra-granular crystalline defects, which are the preferredsites for nucleation.

A slow cooling or isothermal holding is then required to promote theparticles precipitation. Finally, a rapid quench is applied to keep afully austenitic matrix.

FIG. 5 illustrates an exemplary fabrication schedule for the productionof steel compositions/components according to the present disclosure. Assuch, FIG. 5 is a schematic drawing of an exemplary steel fabricationmethod of the present disclosure. As shown in FIG. 5, T_(nr) is theaustenite recrystallization stop temperature, and A_(s) is the austenitestart temperature.

In exemplary embodiments, the TMCP methods have a synergistic effect ofmicro-alloy additions. Depending on the alloying elements to beadded/utilized in the composition, the appropriate thermo-mechanicalconditions should be selected in order to produce the desired fineparticles. In general, the alloying elements utilized in the methods ofthe present disclosure can have some effect on either the TMCP, or thebulk property modification, or both.

In certain embodiments, carbon is the one of the most effective alloyingelements to control the bulk deformation mechanism, promote carbideprecipitation and stabilize the austenite phase during cooling. It isnoted that the total carbon content of the compositions could be muchlarger or higher compared to conventional high manganese steel, but theamount of carbon in solution after TMCP steps should be controlled to amuch lower level.

In exemplary embodiments, manganese is the austenite phase stabilizer.This element can be mainly added to the compositions to maintain a fullyaustenitic matrix during cooling and TMCP. In general, it has littleeffect on the deformation mechanism.

Chromium is a carbide former. It will promote different types ofcarbide, such as M7C and M23C6, depending on the alloy level and/orthermal treatment temperature. Moreover, chromium addition is typicallyimportant for corrosion resistance enhancement.

Niobium and titanium are effective elements to retard therecrystallization during TMCP by forming strain induced (e.g., Ti, Nb C,N) precipitation on the deformed austenite. In addition, the niobiumand/or titanium addition facilitates the bulk carbon concentrationmodification according to exemplary embodiments of the presentdisclosure.

Aluminum and silicon are added to tune or adjust the SFE of the highmanganese steel of the present disclosure. It is noted that aluminumaddition can facilitate quasi-crystalline phase formation, as discussedbelow.

Quasi-Crystal Precipitation Hardened High Mn Steels

It is another object of the present disclosure to provide high Mn steelsutilizing precipitation hardening of quasi-crystals. In exemplaryembodiments, high Mn steels can be strengthened by the precipitation ofquasi-crystals, and such structures can be achieved by heat treating atelevated temperatures (e.g., up to about 700° C.).

In general, quasi-crystalline materials have periodic atomic structures(e.g., 5-fold or 10-fold rotational symmetry), but usually do notconform to the 3-D symmetry typical of ordinary crystalline materials.Due to their crystallographic structure, quasi-crystalline materialswith tailored chemistry exhibit unique properties, which are attractivefor the strengthening of high Mn steels.

It is noted that the quasi-crystalline precipitates can provide higherstrengthening effects than that of crystalline precipitates (e.g.,carbides), because of the difficulty of dislocations to move throughquasi-crystal lattices. Furthermore, quasi-crystals usually will notgrow beyond certain sizes unlike crystalline precipitates, therebyalleviating over-aging concerns associated with certain crystallineprecipitates.

Quasi-crystal materials typically provide non-stick surface propertiesdue to their low surface energy (e.g., about 30mJ/m²) on stainless steelsubstrates in icosahedral Al—Cu—Fe chemistries. Due to their low surfaceenergy, quasi-crystal materials exhibit a low friction coefficient(e.g., about 0.05) in scratch tests with diamond indentor in dry air,combined with relatively high micro-hardness. Quasi-crystallinematerials are found in Al-TM (TM=transition metals; e.g., V, Cr, Mn),Al—(Mn, Cu, Fe)—(Si), and Al—Cu-TM (e.g., Cr, Fe, Mn, Mo) systems.

Ultrafine Grained High Mn Steels

In exemplary embodiments, improved steel compositions (e.g., ultrafinegrained high Mn steel compositions) can be fabricated by exemplarythermo-mechanical controlled processes (TMCP). In certain embodiments,especially in lower Mn alloying chemistry such as 8 wt. % or less inwhich ferrite or martensite phase is thermodynamically more stable thanthe austenite phase, the TMCP of the present disclosure includes heavyplastic deformation at ambient (e.g., 18-24° C.) or cryogenic (e.g.,−196° C.) or intermediate temperature to induce martensite formation,and subsequent annealing at elevated temperatures to reversedeformation-induced martensite into ultrafine grained austenite. Anexemplary thermo-mechanical controlled process is schematically shown inFIG. 6. FIG. 6 depicts a schematic of an exemplary fabrication methodfor producing ultrafine grained high Mn steels according to the presentdisclosure. As shown in FIG. 6, Af is the austenite finish temperature(austenite recrystallization stop temperature), and A_(s) is theaustenite start temperature.

In exemplary embodiments and after heating and holding the steelcomposition at a normalizing temperature, the metastable austenite phaseof the steel composition is transformed to a strain-induced martensitephase by heavy plastic deformation at ambient (e.g., 18-24° C.) orcryogenic (e.g., −196° C.) or intermediate temperatures (FIG. 6). Thestrain-induced martensite phase may be further heavily deformed todestroy lath or plate structures prior to a reversion treatment (e.g.,reversion annealing in FIG. 6). The strain-induced martensite phase maybe reverted to the austenite phase at temperatures low enough tosuppress the grain coarsening of the reverted austenite phase. Inexemplary embodiments, the chemistry of the steel compositions of thepresent disclosure (e.g., high Mn steel compositions) can be tailored sothat the martensite start temperature (M_(s)) of reverted austenite isbelow room temperature (e.g., 18-24° C.).

Exemplary Methods for Fabrication

The present disclosure provides for a method for fabricating a ferrousbased component including: a) providing a composition having from about5 to about 40 weight % manganese, preferably from about 9 to about 25weight % manganese, even more preferably from about 12 to about 20weight % manganese, and from about 0.01 to about 1.2 weight % carbon,preferably from about 0.3% to about 1.2 weight % carbon, even morepreferably from about 0.3% to about 0.7 weight % carbon, and the balanceiron, b) heating the composition to a temperature above the austeniterecrystallization stop temperature of the composition (e.g., to atemperature to homogenize the composition); c) deforming the compositionwhile the composition is at a temperature below the austeniterecrystallization stop temperature of the composition; and d) quenchingor accelerated cooling the composition.

The present disclosure provides for a method for fabricating a ferrousbased component wherein after step d), the matrix of the composition ispredominantly or substantially in the austenitic phase. In one or moreembodiments, the volume percent of austenite in the steel composition isfrom about 50 wt % to about 100 wt %, more preferably from about 80 wt %to about 99 wt %.

The steel composition is preferably processed into predominantly orsubstantially austenitic plates using a hot rolling process. In one ormore embodiments, a steel billet/slab from the compositions described isfirst formed, such as, for example, through a continuous castingprocess. The billet/slab can then be re-heated to a temperature (“reheattemperature”) within the range of about 1,000° C. to about 1,300° C.,more preferably within the range of about 1050° C. to 1250° C., evenmore preferably within the range of about 1100° C. to 1200° C.Preferably, the reheat temperature is sufficient to: (i) substantiallyhomogenize the steel slab/composition, (ii) dissolve substantially allthe carbide and/or carbonitrides, when present, in the steelslab/composition, and (iii) establish fine initial austenite grains inthe steel slab/composition.

The re-heated slab/composition can then be hot rolled in one or morepasses. In exemplary embodiments, the reheated slabs/billets can becooled to the rolling start temperature. In one or more embodiments, therolling start temperature is above 1100° C., preferably above 1080° C.,even more preferably above 1050° C.

In exemplary embodiments, the final rolling for plate thicknessreduction can be completed at a “finish rolling temperature”. In one ormore embodiments, the finish rolling temperature is above about 700° C.,preferably above about 800° C., more preferably about 850° C.Thereafter, the hot rolled plate can be cooled (e.g., in air) to a firstcooling temperature or accelerated cooling start temperature (“ACST”),at which an accelerated cooling starts to cool the plates at a rate ofat least about 10° C. per second to a second cooling temperature oraccelerated cooling finish temperature (“ACFT”). After the cooling tothe ACFT, the steel plate/composition can be cooled to room temperature(e.g., ambient temperature) in ambient air. Preferably, the steelplate/composition is allowed to cool on its own to room temperature.

In one or more embodiments, the ACST is about 750° C. or more, about800° C. or more, about 850° C. or more, or about 900° C. or more. In oneor more embodiments, the ACST can range from about 700° C. to about1000° C. In one or more embodiments, the ACST can range from about 750°C. to about 950° C. Preferably, the ACST ranges from a low of about 650°C., 700° C., or 750° C. to a high of about 900° C., 950° C., or 1000° C.In one or more embodiments, the ACST can be about 750° C., about 800°C., about 850° C., about 890° C., about 900° C., about 930° C., about950° C., about 960° C., about 970° C., about 980° C., or about 990° C.

In one or more embodiments, the ACFT can range from about 0° C. to about500° C. Preferably, the ACFT ranges from a low of about 0° C., 10° C.,or 20° C. to a high of about 150° C., 200° C., or 300° C.

Without being bound by any theory, it is believed that the rapid cooling(e.g., more than about 10° C./sec cooling rate) to the low acceleratedcooling finish temperature (“ACFT”) retards at least a portion of thecarbon and/or nitrogen atoms from diffusing from the austenite phase ofthe steel composition to the grain boundary or second phase. It isfurther believed that the high accelerated cooling start temperature(“ACST”) retards at least a portion of the carbon and/or nitrogen atomsfrom forming precipitates such as, for example, carbides, carbonitrides,and/or nitrides during subsequent cooling to the ACFT. As such, theamount of precipitates at the grain boundaries is reduced. Therefore,the steel's fracture toughness and/or resistance to cracking isenhanced.

Following the rolling and cooling steps, the plate can be formed intopipes or the like (e.g., linepipe). Any suitable method for forming pipecan be used. Preferably, the precursor steel plate is fabricated intolinepipe by a conventional UOE process or JCOE process which is known inthe art.

EXAMPLES

The present disclosure will be further described with respect to thefollowing examples; however, the scope of the disclosure is not limitedthereby. The following examples illustrate improved systems and methodsfor fabricating or producing improved steel compositions (e.g., improvedhigh Mn steel compositions having enhanced wear and/or deformationresistance at cryogenic temperatures or the like). As illustrated in thebelow examples, the present disclosure illustrates that the advantageoussteel compositions/components of the present disclosure improve one ormore of the following properties: strength, toughness, elastic modulus,thermal expansion coefficient and/or thermal conductivity. In general,the yield strength/cryogenic toughness/thermal stress of the steels ofthe present disclosure can be improved/increased through the control ofmicrostructure and/or chemistry. As noted, some possible routes includepromoting phase transformations (e.g., to martensite or epsilon phases),twinning during deformation, and/or introducing hard erosion resistantsecond phase particles to the compositions.

In exemplary embodiments, the present disclosure provides for a ferrousbased component fabricated according to the steps comprising: a)providing a composition having from about 5 to about 40 weight %manganese, from about 0.01 to about 1.2 weight % carbon, and the balanceiron; b) heating the composition to a temperature above the austeniterecrystallization stop temperature of the composition; c) cooling thecomposition to a temperature below the austenite recrystallization stoptemperature of the composition; d) deforming the composition while thecomposition is at a temperature below the austenite recrystallizationstop temperature of the composition; and e) quenching the composition.

Example 1: Fabrication of High Mn Steels of the Present Disclosure

In one exemplary embodiment of the disclosure, steel plates having thechemistry shown in Table 2 are fabricated by vacuum induction meltingand hot rolling. Steel plates with 25 mm thickness were fabricated byfinish rolling at around 850° C. followed by accelerated cooling to roomtemperature.

TABLE 2 Chemistry of inventive steels (weight percent) Steel C Si Mn CrMo Ti Nb Cu V N EM501 0.605 0.150 17.53 3.12 — — — 0.50 — — EM502 0.6000.132 18.30 3.03 — — 0.024 0.50 — — EM503 0.611 0.138 18.03 3.01 — 0.0210.023 0.50 — 0.015 EM504 0.620 0.154 18.10 3.01 — 0.017 0.023 0.50 —0.022 EM505 0.600 0.124 18.20 2.98 — — 0.020 0.50 0.097 — EM506 0.5870.160 18.02 2.98 0.52 0.083 0.022 0.50 — —

Example 2: Mechanical Properties of High Mn Steels of the PresentDisclosure

Tables 3 and Table 4 show the mechanical properties of inventive steelsat cryogenic temperature and ambient temperature (around 25° C.),respectively. All of the steel plates were characterized by minimumyield strength ranging from about 600 MPa to 630 MPa at ambienttemperature in the as-rolled condition without cold deformation.

TABLE 3 Cryogenic mechanical properties of inventive steels. CryogenicMechanical Properties @ −164° C. Charpy 0.2% Yield Ultimate ElasticReduction Impact Sample Strength Tensile Strength Modulus Elongation ofArea Energy @ ID (MPa) (MPa) (GPa) (%) (%) −196° C. (J) EM501 880 1508185.5 48 37 67.3 EM502 802 1500 177.9 48 34 76.8 EM503 821 1489 180.0 5048 73.2 EM504 799 1518 184.8 49 46 74.1 EM505 776 1499 181.3 50 48 70.5EM506 732 1417 160.0 45 30 56.9

TABLE 4 Ambient temperature mechanical properties of inventive steels.Room Temperature Mechanical Properties @ 25° C. Charpy 0.2% YieldUltimate Elastic Reduction Impact Sample Strength Tensile StrengthModulus Elongation of Area Energy @ ID (MPa) (MPa) (GPa) (%) (%) −40° C.(J) EM501 598 1085 143.0 57 — 119.4 EM502 611 1077 150.2 55 — 112.0EM503 618 1086 156.5 61 — 112.8 EM504 630 1090 134.8 55 — 128.7 EM505625 1081 147.6 54 — 106.9 EM506 624 1095 157.6 54 — 89.8

Table 5 shows the average coefficient of thermal expansion (CTE), andmechanical properties of inventive steels. The measurement of CTE weremade with a LVDT (linear variable differential transducer)-based quartzdilatometer measurement system (ASTM standard E228). The change ofspecimen length has been recorded as the temperature was cycled between−196° C. and 25° C. at a maximum rate of 2° C./minute. T-typethermocouples were used for temperature measurement in the dilatometer.The CTE (α) were calculated as follows:

$\alpha_{t\; 12} = \frac{\left\{ {\left( {L_{t\; 2} - L_{t\; 1}} \right)/L_{0}} \right\}}{T_{t\; 2} - T_{t\; 1}}$

where L_(t1) and L_(t2) are the measured displacements of the specimensat time t₁, and t₂ respectively;

T_(t1) and T_(t2) are the measured temperatures of the specimens at timet₁, and t₂ respectively; and

L₀ is the initial specimen length

The average CTE values were calculated as a secant slope based of theend points of the polynomial regression from −196° C. and 25° C. Elasticmodulus at cryogenic temperature and 0.2% yield stress at ambienttemperature were used for the calculation of thermal stress usingEquation (1). The inventive steels showed thermal stress lower than 50%of their yield strength.

TABLE 5 Average coefficient of thermal expansion and mechanicalproperties of inventive steels. Average Thermal 0.2% Thermal ExpansionElastic Thermal Yield Stress/ Coefficient Modulus Stress Strength 0.2%Yield Steel (10⁻⁶ m/m ° C.) (GPa) (MPa) (MPa) Strength EM501 8.5 185.5299.5 598 0.50 EM502 8.1 177.9 273.8 611 0.45 EM503 8.5 180.0 290.6 6180.47 EM504 8.3 184.8 291.4 630 0.46 EM505 7.9 181.3 272.2 625 0.44 EM5068.1 160.0 246.2 624 0.46

Without being bound by any theory, it is noted that an increase incarbon content in the high Mn steel matrix enhances the mechanicalstrength of the steel and the work hardening rate. In exemplaryembodiments, Mn alloying in the range of about 12-20 weight % of thetotal composition stabilizes the austenite phase, and increases thecarbon solubility in the steel matrix. The Cr alloying up to about 3weight % increases the corrosion resistance and the mechanical strengthby solution strengthening. The Cu alloying of about 0.5 to about 2weight % increases carbon solubility and corrosion resistance.

In exemplary embodiments, the (TMCP) hot rolling parameters can beadjusted to obtain steel compositions having a refined grain sizes ofabout 200 μm or less, and/or low carbide precipitate fractions of about5 volume % or less. The methods may include a finish rolling step orsteps at lower temperatures, which would introduce deformationbanding/dislocations tangles to thereby enhance the formation of fineintra-grain precipitates.

The exemplary modified TMCP hot rolling steps/parameters can be combinedwith the addition of various micro-alloying elements such as, withoutlimitation, V, Nb, Ti, Mo and/or N. It has been found that themicro-alloying elements in high Mn steels can result in the formation offine carbide/nitride/carbo-nitride precipitates finely dispersed in thesteel matrix. The finely dispersed precipitates can retard graincoarsening during reheating and recrystallization during hot rolling,which thereby advantageously enhances the strength of the steelcompositions/components of the present disclosure.

PCT/EP Clauses

1. A method for fabricating a ferrous based component comprising: a)providing a composition having from 5 to 40 weight % manganese, from0.01 to 1.2 weight % carbon, and the balance iron; b) heating thecomposition to a temperature above the austenite recrystallization stoptemperature of the composition or to a temperature to homogenize thecomposition; c) cooling the composition to a temperature below theaustenite recrystallization stop temperature of the composition; d)deforming the composition while the composition is at a temperaturebelow the austenite recrystallization stop temperature of thecomposition; and e) quenching the composition.

2. The method of clause 1, wherein after step e), the carbideprecipitate fraction volume of the composition is 5 volume % or less ofthe composition.

3. The method of clauses 1 or 2, wherein after step e), the compositionhas a microstructure having a refined grain size of 100 μm or less.

4. The method of clause 3, wherein the microstructure having a refinedgrain size of 100 μm or less includes a surface layer of thecomposition; wherein the thickness of the surface layer is from 10 nm to5000 nm; and wherein the surface layer is formed prior to or during useof the composition.

5. The method of clause 4, wherein the surface layer is formed via asurface deformation technique selected from the group consisting of shotpeening, laser shock peening, surface burnishing and combinationsthereof.

6. The method of any one of clauses 1-5, wherein prior to step e), thecomposition is slowly cooled or isothermally held; and wherein step e)includes rapidly quenching the composition.

7. The method of any one of clauses 1-6, wherein step d) includesdeforming the composition while the composition is at a temperaturebelow the austenite recrystallization temperature and above themartensite transformation start temperature.

8. The method of any one of clauses 1-7, wherein step d) includesdeforming the composition to induce martensite formation of thecomposition; wherein the composition is deformed at a temperature offrom 18° C. to 24° C. to induce martensite formation of the composition;and further comprising, after step d), heating the composition to atemperature above the austenite recrystallization stop temperature;wherein heating the composition to a temperature above the austeniterecrystallization stop temperature after step d) reversesdeformation-induced martensite of the composition into ultrafine grainedaustenite; and wherein the martensite start temperature of the ultrafinegrained austenite is below 24° C.

9. The method of any one of clauses 1-8, further comprising, after stepe), heating the composition to a temperature above the austeniterecrystallization stop temperature, and then quenching the composition.

10. The method of any one of clauses 1-9, further comprising, prior tostep c), deforming the composition while the composition is at atemperature above the austenite recrystallization stop temperature.

11. The method of any one of clauses 1-10, wherein step c) includescooling the composition at a rate of from 2° C. per second to 60° C. persecond.

12. The method of any one of clauses 1-11, wherein the compositionfurther includes one or more alloying elements selected from the groupconsisting of chromium, aluminum, silicon, nickel, cobalt, molybdenum,niobium, copper, titanium, vanadium, nitrogen, boron, zirconium, hafniumand combinations thereof.

13. The method of clause 12, wherein the chromium ranges from 0.5 to 30weight % of the total composition; wherein each of the nickel or cobaltranges from 0.5 to 20 weight % of the total composition; wherein thealuminum ranges from 0.2 to 15 weight % of the total composition;wherein each of the molybdenum, niobium, copper, titanium or vanadiumranges from 0.01 to 10 weight % of the total composition; wherein thesilicon ranges from 0.1 to 10 weight % of the total composition; whereinthe nitrogen ranges from 0.001 to 3.0 weight % of the total composition;wherein the boron ranges from 0.001 to 0.1 weight % of the totalcomposition; and wherein each of the zirconium or hafnium ranges from0.2 to 6 weight % of the total composition.

14. The method of any one of clauses 1-13, wherein the compositionincludes from 8 to 20 weight % manganese, from 0.30 to 0.7 weight %carbon, from 0.5 to 3 weight % chromium, from 0.5 to 2.0 weight %copper, from 0.1 to 1 weight % silicon, and the balance iron.

15. A ferrous based component fabricated according to the stepscomprising: a) providing a composition having from 5 to 40 weight %manganese, from 0.01 to 1.2 weight % carbon, and the balance iron; b)heating the composition to a temperature above the austeniterecrystallization stop temperature of the composition; c) cooling thecomposition to a temperature below the austenite recrystallization stoptemperature of the composition; d) deforming the composition while thecomposition is at a temperature below the austenite recrystallizationstop temperature of the composition; and e) quenching the composition.

Whereas the disclosure has been described principally in connection withsteel compositions for use in components for material conveying systems,fluids/solids transport systems, mining operations, oil sand pipingsystems, earth-moving equipment, drilling components, and/oroil/gas/petrochemical applications, such descriptions have been utilizedonly for purposes of disclosure and are not intended as limiting thedisclosure. To the contrary, it is to be recognized that the disclosedsteel compositions are capable of use in a wide variety of applications,systems, operations and/or industries.

Although the systems and methods of the present disclosure have beendescribed with reference to exemplary embodiments thereof, the presentdisclosure is not limited to such exemplary embodiments and/orimplementations. Rather, the systems and methods of the presentdisclosure are susceptible to many implementations and applications, aswill be readily apparent to persons skilled in the art from thedisclosure hereof. The present disclosure expressly encompasses suchmodifications, enhancements and/or variations of the disclosedembodiments. Since many changes could be made in the above constructionand many widely different embodiments of this disclosure could be madewithout departing from the scope thereof, it is intended that all mattercontained in the drawings and specification shall be interpreted asillustrative and not in a limiting sense. Additional modifications,changes, and substitutions are intended in the foregoing disclosure.Accordingly, it is appropriate that the appended claims be construedbroadly and in a manner consistent with the scope of the disclosure.

1. A method for fabricating a ferrous based component comprising: a)providing a composition having from 5 to 40 weight % manganese, from0.01 to 1.2 weight % carbon, and the balance iron; b) heating thecomposition to a temperature above the austenite recrystallization stoptemperature of the composition or to a temperature to homogenize thecomposition; c) cooling the composition to a rolling start temperature;d) deforming the composition while the composition is at a temperaturebelow the austenite recrystallization stop temperature of thecomposition; and e) quenching the composition.
 2. The method of claim 1,wherein step c) includes cooling to a temperature below the T_(nr)temperature.
 3. The method of claim 1, wherein after step e), thecarbide precipitate fraction volume of the composition is 5 volume % orless of the composition.
 4. The method of claim 1, further comprisingafter step e) a surface deformation step selected from the groupconsisting of shot peening, laser shock peening, surface burnishing andcombinations thereof.
 5. The method of claim 1, wherein step e) includesrapidly quenching the composition.
 6. The method of claim 1, furthercomprising, after step e), heating the composition to a temperatureabove the austenite recrystallization stop temperature, and thenquenching the composition.
 7. The method of claim 1, further comprising,prior to step c), deforming the composition while the composition is ata temperature above the austenite recrystallization stop temperature. 8.The method of claim 7, wherein the composition is deformed at atemperature of from 700° C. to 1000° C.
 9. The method of claim 1,wherein step b) includes heating the composition to at least 1000° C.10. The method of claim 1, wherein step c) includes cooling thecomposition at a rate of from 2° C. per second to 60° C. per second. 11.The method of claim 1, wherein the composition further includes one ormore alloying elements selected from the group consisting of chromium,aluminum, silicon, nickel, cobalt, molybdenum, niobium, copper,titanium, vanadium, nitrogen, boron, zirconium, hafnium and combinationsthereof.
 12. The method of claim 11, wherein the chromium ranges from0.5 to 30 weight % of the total composition; wherein each of the nickelor cobalt ranges from 0.5 to 20 weight % of the total composition;wherein the aluminum ranges from 0.2 to 15 weight % of the totalcomposition; wherein each of the molybdenum, niobium, copper, titaniumor vanadium ranges from 0.02 to 10 weight % of the total composition;wherein the silicon ranges from 0.01 to 10 weight % of the totalcomposition; wherein the nitrogen ranges from 0.01 to 3.0 weight % ofthe total composition; wherein the boron ranges from 0.001 to 0.1 weight% of the total composition; and wherein each of the zirconium or hafniumranges from 0.2 to 6 weight % of the total composition.
 13. The methodof claim 1, wherein the composition includes from 8 to 20 weight %manganese, from 0.3 to 0.7 weight % carbon, from 0.5 to 3 weight %chromium, from 0.5 to 2.0 weight % copper, from 0.1 to 1 weight %silicon, and the balance iron.
 14. A ferrous based component fabricatedaccording to the steps comprising: a) providing a composition havingfrom 5 to 40 weight % manganese, from 0.01 to 1.2 weight % carbon, andthe balance iron; b) heating the composition to a temperature above theaustenite recrystallization stop temperature of the composition; c)cooling the composition to a temperature below the austeniterecrystallization stop temperature of the composition; d) deforming thecomposition while the composition is at a temperature below theaustenite recrystallization stop temperature of the composition; and e)quenching the composition.
 15. The ferrous based component of claim 14,wherein after step e), the carbide precipitate fraction volume of thecomposition is 5 volume % or less of the composition.
 16. The ferrousbased component of claim 15, further comprising after step e) a surfacedeformation step selected from the group consisting of shot peening,laser shock peening, surface burnishing and combinations thereof. 17.The ferrous based component of claim 14, wherein step e) includesrapidly quenching the composition.
 18. The ferrous based component ofclaim 14, further comprising, after step e), heating the composition toa temperature above the austenite recrystallization stop temperature,and then quenching the composition.
 19. The ferrous based component ofclaim 14, further comprising, prior to step c), deforming thecomposition while the composition is at a temperature above theaustenite recrystallization stop temperature.
 20. The ferrous basedcomponent of claim 19, wherein the composition is deformed at atemperature of from 700° C. to 1000° C.
 21. The ferrous based componentof claim 14, wherein step b) includes heating the composition to atleast 1000° C.
 22. The ferrous based component of claim 14, wherein stepc) includes cooling the composition at a rate of from 2° C. per secondto 60° C. per second.
 23. The ferrous based component of claim 14,wherein the composition further includes one or more alloying elementsselected from the group consisting of chromium, aluminum, silicon,nickel, cobalt, molybdenum, niobium, copper, titanium, vanadium,nitrogen, boron, zirconium, hafnium and combinations thereof.
 24. Theferrous based component of claim 23, wherein the chromium ranges from0.5 to 30 weight % of the total composition; wherein each of the nickelor cobalt ranges from 0.5 to 20 weight % of the total composition;wherein the aluminum ranges from 0.2 to 15 weight % of the totalcomposition; wherein each of the molybdenum, niobium, copper, titaniumor vanadium ranges from 0.02 to 10 weight % of the total composition;wherein the silicon ranges from 0.01 to 10 weight % of the totalcomposition; wherein the nitrogen ranges from 0.01 to 3.0 weight % ofthe total composition; wherein the boron ranges from 0.001 to 0.1 weight% of the total composition; and wherein each of the zirconium or hafniumranges from 0.2 to 6 weight % of the total composition.
 25. The ferrousbased component of claim 14, wherein the composition includes from 8 to20 weight % manganese, from 0.30 to 0.7 weight % carbon, from 0.5 to 3weight % chromium, from 0.5 to 2.0 weight % copper, from 0.1 to 1 weight% silicon, and the balance iron.